@przemo1986@leo-idt Hello, the reason is that ECMWF contains forecast for thunderstorms, therefore we display them. But the rest of the models does not have this data, so we do not display thunderstorm symbols.
a. Which shaded area are you referring? In Meteogram the explanation is given in posts here above.
b. Check High, Medium and Low clouds layers. If necessary see More layers... The direction of the sun is given by a plugin only available on website. Menu > Install plugins > Sun position
c. You probably mean in case of temperature inversion, which brings a cloud / fog layer below the inversion. You can check that by using the Sounding feature. Right click on mouse.
Temperature inversion when the temperature (red curve) is increasing with altitude instead of decreasing.
Clouds when temperature and dew point are close together (red and blue curves)
Note that the weather model can only show this phenomenon at large scale but not in local conditions like in a mountain valley.